In the process for manufacturing a semiconductor device, comprising the steps of forming interconnection-shaped recesses on a surface of the insulating film on a semiconductor substrate, sedimenting a metal film made of copper or the like on the insulating film having the recesses, and subjecting the metal film to polishing treatment by a polishing device and a polishing liquid, thereby allowing the metal layer to remain only in the recesses to form a metal interconnection layer, wherein Metal Chemical Mechanical Polishing (hereinafter simply referred to as “metal CMP”) is employed for the process of polishing.
However, in the metal CMP, there arise grooves so-called dishing on the metal interconnection layer in the recesses of the insulating film, so that the cross-sectional area of the metal interconnection layer is reduced, thereby causing an increase in electric resistivity. This dishing is caused by more excessive polishing or etching of the surface of the metal interconnection layer than that of the insulating film surface by the polishing liquid composition. Especially copper, one of the main metal interconnection, has defects of being excessively etched by the polishing liquid composition, so that the dishing is likely to be caused.
Therefore, there has been desired a polishing liquid composition free from defects such as dishing in the metal layer during the formation of interconnection, with retaining an etching action for polishing the metal film on the insulating film.
As a conventional polishing liquid, for instance, Japanese Patent Laid-Open Nos. Hei 8-83780 and Hei 11-21546 each discloses a polishing liquid comprising benzotriazole or a derivative thereof as a protective film-forming agent for the metal surface in order to prevent the dishing. Since the formed protective film is rigid, when the metal layer is polished in the metal CMP, the polishing speed would become insufficient. In addition, Japanese Patent Laid-Open No. Hei 11-116942 discloses a composition for polishing, comprising a compound having 1 to 10 alcoholic hydroxyl groups, or a nitrogen-containing basic compound having 1 to 10 alcoholic hydroxyl groups. This composition for polishing has a purpose of reducing particles deposited on a wafer surface in final polishing of the semiconductor wafer, so that the problems to be solved are different.
In addition, Japanese Patent Laid-Open No. Hei 10-44047 discloses a polishing liquid comprising an aqueous medium, an abrasive, an oxidizing agent, and an organic acid. However, since the etching action is too strong, the prevention for dishing would be insufficient. Further, Japanese Patent Laid-Open No. Hei 11-195628 discloses a process for polishing in which a polishing liquid is used in combination with ammonium polyacrylate as a substance for suppressing oxidation and etching. However, in the metal CMP in which a metal layer made of copper or the like is polished, there arises surface roughening of the copper surface caused by ammonium polyacrylate.
An object of the present invention is to provide a polishing liquid composition capable of maintaining a polishing speed of a metal film, suppressing an etching speed, and having an excellent prevention effect such as dishing of the metal interconnection layer, in a surface to be polished comprising an insulating layer and a metal layer; a process for polishing; and a process for manufacturing a semiconductor substrate.
These objects and other objects of the present invention will be apparent from the following description.